305 on a 9.5in rim

a buddy of mine runs a 315 sumitomo on his 17x9 03 Cobra wheel, whatever that's worth

I have 285s on a 9in rim and I think it's a perfect fit...little bit of buldge but not too much. I would go with 295s on a 9.5in. 305s would work but it might buldge too much, plus not all shops will want to do it.

Good data:
http://www.tirerack.com/tires/tiretech/tirespecskey.jsp

"A tire mounted on a narrow rim would be "narrower" than if the same size tire was mounted on a wide rim...Because of the different wheel widths used in the above example, there is a 8/10" projected difference in tire section width when comparing a tire mounted on the narrowest rim to the widest rim within its range. "

http://www.dunloptires.com/care/widthRatio.html

"Correct rim width ensures flex at the designed flex point in a tire sidewall for optimum tire performance.
If the rim is too narrow, the flex point moves toward the shoulder area, creating heat buildup in the shoulder, which reduces tire life and could result in failure."

http://www.yokohamatire.com/utrimwidth.asp

http://www.yokohamatire.com/utwheels.asp

"Choosing a wider rim: increases vehicular stability, steering response and cornering ability. A rule of thumb is to use a rim width 90% as wide as the tread width (not section width) of a performance tire for street applications. This provides a good balance between performance and ride quality. Always be sure that the chosen rim width is within the tire's range of acceptable rim width specifications."

So many Mustang owners put oversized tires on their rims and say it handles better. It a delusional claim. I have done it and ended up regretting it. It's a sloppier ride, no ifs ands or buts. There are no performance street cars that have such a disparity between rim and tire widths and there is a real, proven reason for it. That's why rims are available in different widths. A smart tire shop won't mount a 295/305/315 on a 9" rim because it's a liability.

Oversized tires is right along the lines of a huge aluminum wing on a stock Civic - you may think it looks good but don't claim any performance benefit becuase it's strictly ornamental, and in the end, only hurts all-around performance.

yeah i know a lot of the terminator guys run 315's on the stock 9s fwiw

I think 285s or 295s would be good for a 9.5 inch rim. I ran 275s on my 9s and 315 on the 10.5s. Looked pissa and filled the well perfectly.

What kind of tires are you going to run? Some have a much more narrow footprint then others.

Adam

Therian said:

It's mostly an aesthetics thing. I want to do autocross and open track, but I'm going to want another set of rims and tires for that for several reasons. That said, it's also a price thing...I think I may end up going with 285s due to them being far more affordable.

Click to expand...

285 on a 9.5 is a good choice, it will look good and be functional.

WHen I started reading this post I was thinking 285 myself. But yea coiledskunk hit the nail on the head. I would want at least a 10" for 295-305 and 10.5" for 315. And I say AT LEAST that. Ideally i would go a little wider (like 11") for the 315.

I debated this before replacing tires and the guy at the tire shop said that the biggest he would go on a 9.5 would be 285 due to the bulge. If you think about it, it is like over inflating a normal sized tire where you are only running 50% to 75% of the tread in middle of the tire... You are only going to loose traction not gain anything... Plus, not too many places are going to mount a 305 tire on a 9.5 rims due to safety issues and the bead seal...